1. Field of the Invention
The present invention relates to a permanent magnet motor, a position estimation apparatus and a motor drive control apparatus.
2. Description of the Related Art
Conventionally, a permanent magnet motor which does not consume energy for a magnetic field is widely used as a high-efficiency motor (Patent Document 1). The permanent magnet motor, especially an interior permanent magnet (IPM) motor in which a permanent magnet is embedded in a rotor, has a property (characteristic) called a salient pole property in which a coil inductance changes according to the rotor angle. Because of the salient pole property, the IPM motor, being capable of using not only a magnetic torque due to the magnetic flux of the permanent magnet but also a reluctance torque due to the salient pole property, is highly efficient and has a wide use-speed range, and thus, the application range of the IPM motor is expanding these days.
Further, the IPM motor is also used in a sensor-less angle estimation in which the rotor angle is estimated without using a rotation sensor, by using the salient pole property.